71 K20 gearbox, transfer case and rear diff questions

[NZBurb]

Hi everyone.

I have a 71 GMC K20 and am looking to do some work on the drive train. Things are starting to get a bit loose and extra noisy and I figure with living in New Zealand (where parts are non-existent) I thought I might as well replace the drive train in one go and get her running tip-top for a number of years. I have been doing some research on providers however I thought my good friends I'd reach out to hear your thoughts on reputable vendors I can contact for reconditioned/new:

1. NV4500 (and any recommendations on clutches would be great) to replace the TH350

2. Transfer case (NP205)

3. Whole rear (eight lug, drum) - I currently have a Eaton HO52 and am looking to replace the whole rear end (given the difficulty in finding parts) with something where parts are a bit more readily available, e.g. Dana 60 or 14 bolt.

Thanks very much - I really appreciate the knowledge on here and I definitely owe you all some photos!

Thanks,
Vaughan